The objective of this proposal is to evaluate how animals learn about odors and odor mixtures. All animals, including humans, must learn to attend to the most relevant aspects of sensory stimuli. In regard to odors, the relevant aspect is sometimes complex configurations (mixtures) of many individual odorant molecular types. Yet at other time individual elements or submixtures provide the most relevant biological information, and these elements must be detected against complex and variable background odors. The honey bee is an excellent model animal to use to evaluate how animals in general solve these problems. Honey bee workers readily learn to associate an odor with brief reinforcement. Furthermore, they can team solve both elemental and configural learning problems in a behavioral paradigm that permits rigorous control of stimulation and physiological manipulation. This work will have general applicability to biomedical research because of the anatomical and physiological similarity of the insect peripheral olfactory processing neuropils to those of humans. These similarities may have arisen via convergent evolution, which implies an important functional analogy between invertebrate and mammalian olfactory processing. Thus use of an animal such as the honey bee stands to highlight important functional hypotheses that can be generally tested in mammals. The work outlined in the proposal will evaluate theoretical predictions that stem from models of elemental learning in stimulus mixtures. In addition, pharmacological manipulation of the Antennal Lobe, which is the functional analog to the mammalian Olfactory Bulb, will be used to test predictions about how odors are represented in that neuropil.